1. Field of the Invention
The invention relates to a method for the operation of a thread supplying apparatus of a weaving machine.
2. Description of the Prior Art
An exemplary embodiment of the most common kind of a thread supplying apparatus, which serves for the intermediate storage of a weft thread, is known from the patent specification EP 0 811 573 A2. For inserting a weft thread into a shed which is formed by a weaving machine the weft thread is, as is known, drawn off from a supply bobbin, a specific weft thread length is stored on the intermediate storage of the thread supplying apparatus, and the weft thread is then inserted into the shed with the help of a projectile or a rapier.
In the operation of a thread supplying apparatus of this kind there arises the problem that the draw-off tension of the weft thread which is stored on the intermediate storage depends on the winding speed of a wind-up member, which serves to wind the weft thread onto a storage drum of the thread supplying apparatus. With increasing winding speed the draw-off resistance of the weft thread from the intermediate storage increases. If the weft thread is applied to the storage drum of the thread supplying apparatus with a high winding speed, whether this be caused by a brief rapid winding up of weft threads and/or by a high speed of rotation of the weaving machine with a correspondingly large requirement of weft threads and high winding speed, then this results in a high draw-off resistance of the weft thread and an undesirably high thread tension. Disadvantageous in the operation of known thread supplying apparatuses is thus the fact that high thread tensions can arise in the weft thread, which causes a damage to the weft thread and in particular increases the risk of a weft thread breaking.
The object of the present invention is to operate the thread supplying apparatuses of a weaving machine in such a manner that the weft thread is exposed to lower stresses.
The object is in particular satisfied by a method for operating a thread supplying apparatus of a weaving machine in that the weft thread requirement for at least two following weft insertions is transmitted to the thread supplying apparatus at the same time. In a preferred method the information for four, five, eight, twelve or, for example, sixteen weft insertions is transmitted at the same time to the thread supplying apparatus. The thread supplying apparatus thereby has available an advance information in that in addition to the weft thread requirement for the next following weft insertion, the information with respect to the weft thread requirement for at least one further, following weft insertion is present. The thread supplying apparatus can be controlled with the help of this advance information in such a manner that, at the time point of the effective weft thread requirement, sufficient weft thread is located on the storage drum, with the thread supplying apparatus or a control device, which is placed before it and which controls the thread supplying apparatus, controlling the speed of rotation of the wind-up member in such a manner that, for example, the maximum speed of rotation of the wind-up member remains as low as possible, and/or that the acceleration or braking of the wind-up member takes place as slowly as possible. A thread supplying apparatus has, as is for example described in the specification WO 99/14149, a control system with a microprocessor, so that in the presence of advance information the thread supplying apparatus automatically winds the thread onto the storage body and determines the speed of rotation, the acceleration or the braking of the wind-up member automatically and, in particular, in such a manner that the weft thread does not experience too great a mechanical stress.
The method in accordance with the invention thus has the advantage that the weft threads are wound onto the storage drum relatively carefully even at a high weft thread requirement, and that the draw-off resistance of the weft thread lies in a tolerable range, through which the danger of weft thread breakages is reduced.
For the operation of a weaving machine a plurality of thread supplying apparatuses is usually required, which are controlled and monitored by the weaving machine control system. In an advantageous arrangement all thread supplying apparatuses are connected to a common data bus, with a common information signal with respect to the weft thread requirement preferably being delivered to all thread supplying apparatuses. At least the information as to when which thread supplying apparatus has to deliver an amount of weft thread is encoded in this common information signal. Thus each thread supplying apparatus is automatically in a position to wind up the respectively required amount of weft thread onto the storage drum prior to the specified time as a result of the advance information which is contained in the common information signal, with the wind-up member being controlled in such an ideal manner that a low stressing of the weft thread results.
In an advantageous method the common information signal is transmitted anew to all thread supplying apparatuses after each complete weaving machine cycle. This method has the advantage that in the event of a failure, or of a putting back into operation of a thread supplying apparatus, the remaining thread supplying apparatuses, which are capable of functioning, are controlled in such a manner that they make the required amount of weft thread available. Thanks to the advance information which is contained in the common information signal, the respective thread supplying apparatuses which are capable of functioning are in a position to control the wind-up member in such an ideal manner that the required greater or lesser amount of weft threads is available on the respective storage drums, with a high weft thread stressing being avoided.